256 



B. KOTO. 



short description of it, and its wide distribution in the amphibolites 

 from the Waldviertel of Lower Austria. 



Apatite, which is so far not found in the hornblendic zone, 

 is present here in large quantities in the form of grains of nearly the 

 same size as that of the salite. It is not prismatic in habitus as 

 usually found in rocks, and in the present case, one might take it for 

 a light-coloured salite, but its faint-blue ])olarization-colours, its 

 characteristic dot-like enclosures, and its hexagonal cross-section 

 preclude its being confounded with the augitic mineral. 



Lastly, the most interesting component found in the light-green 

 zone is the titanite (Figs. 5, and 6, PI. XXIII). It is not found 

 in well-finished crystals, iDut in those forms resembling rolls of 

 butter (weckenjörmig). Some are spindle-shaped, tapering at both 

 ends into sharp points. Others are approximately s|)henoidal, being 

 fissured transversely at various points across the crystals ; along these 

 fissures and also at fight angles to them lie the directions of maximum 

 extinction. We have here probably a basal view of the titanite. 

 The other very obtuse rliombs are its clinopinacoids with oblique 

 extinctions. There are still others which indicate no signs whatever 

 of crystallogra|)hic forms, but present shapes like falling drops from 

 the melted end of candle-wax. 



In some of these clumps there exists a black, formless mass in 

 the centre, wliich I presume to be a titaniferous iron (Fig. 5). At 

 times the black cores nre of a tolerably large size, and the 

 titanite forms but a very thin coating around them. The titanite 

 is highly refractive, and has dark margins and a chagrined surface, 

 due to the total refraction of lio-ht that enters from the other sides. 

 Its substance is not very clear, and has some enclosures whose 

 nature could not be made out, owing to the high refraction of 

 the titanite. The polarization -colours are rather weak, ranging from 



